Fabric soiling, always a problem with textiles, became even more of a problem with the advent of permanent press fabrics composed of cotton-synthetic blends. These are treated with various additives, which often make them more difficult to clean. In addition, permanent press fabrics are best laundered at low temperatures and mild agitation, whereas soil is best removed at higher temperatures and vigorous agitation. For these reasons, various soil release agents are frequently applied to such fabrics to aid in removing soil during laundering. Preferably, these soil release agents are not themselves removed during laundering (i.e., are durable), and either improve or do not harm other desired properties of the fabric.
Fluorochemicals, despite their comparatively high cost, are probably the most widely used soil release agents on cellulosic fabrics because of their performance at low concentration, their compatibility with permanent press finishes, and freedom from most undesired side effects. However, these agents also tend to affect the hydrophilicity and oleophobicity (i.e., the water and oil repellency) of the fabrics in ways that may be desirable for some applications but undesirable for others. For example, hydrophilic soil releasers are useful to maintain the desired wicking of moisture from skin that fabrics provide, but such hydrophilicity may not be desirable for some other applications such as outerwear. Balancing these characteristics to achieve the desired properties for certain applications while maintaining good soil release properties is often difficult.
A widely used class of soil release fluorochemicals is composed of perfluorinated urethanes containing polyethylene oxide moieties. Such urethanes and their intermediate isocyanates are costly and potentially hazardous to manufacture. The urethane type products are often repellent as well as soil releasing, and thus reduce the comfort of wearing cotton or similar garments. These existing products are difficult to modify when it is desired to increase the degree of hydrophilicity of the fabric for a particular application.
Fluorochemicals which are not urethane based have been used for oil and water repellency in the paper industry. U.S. Pat. No. 5,674,961 of Fitzgerald discloses a class of fluorochemical copolymers useful for improving the water, oil and grease resistance of paper. None of the information in this patent suggests that such a copolymer might be useful as a soil release agent, an entirely different type of application than grease-proofing paper. U.S. Pat. No. 4,147,851 of Raynolds teaches fluorochemical copolymers useful for oil and water repellency applications for paper and fabrics. Again, there is no suggestion that these copolymers are useful as a soil release agent.
Soil release fluorochemicals which are as effective as the perfluorinated urethanes, but which do not involve costly and potentially hazardous isocyanate/urethane chemical manufacturing processes are highly desirable and would have widespread applications. Even more desirably, such a soil release agent would be made by a process, which makes it easier to modify the degree of hydrophilicity of the agent and treated fabric over a wide range to suit various applications. The present invention provides such soil release fluorochemicals.